Yes, you're quite right, cougr.
I thought it was posed as a question.
However, you can have a curve-ball "anything", including a curve-ball "statement" intended to draw/elicit a "desired" response.
A curve-ball (metaphorically speaking) is a ruse, "a deceptive artifice in verbal dealings", designed to catch an unsuspecting person out...i.e., to sus them out as you correctly say.
It is even more deceptive, if you think about it, if it's in the form of a statement, instead of a direct question - it's doubly cloaked, if anything. Venizelos was looking for his statement to be "corrected", or restated (correctly) by the respondent, in order to sus them out. I haven't read the article, I'm just going by what nickel posted.
So a verbal dealing is a sentence, a phrase, a statement, even grunting and pointing meaningfully or suggestively (in the wrong direction).
Venizelos' statement was definitely a curve-ball, but the only shortfall/problem with this term is (if we're looking for one) - it's predominantly American English, but I think it is nevertheless understood, if not used, in other English speaking countries. The English have a ready made equivalent waiting to be coined (if/when they start looking for one), in "late out-swinger", or "yorker", as in - I bowled him a yorker, or a late out-swinger.